function density = getRbDensity(temperature, isotope)
    rb85=Atom.AlkaliMetal.AlkaliMetal('85Rb');
    rb87=Atom.AlkaliMetal.AlkaliMetal('87Rb');
    density85 = Gas.Vapor(rb85, 'temperature', 273.15+temperature).density*1e-6;
    density87 = Gas.Vapor(rb87, 'temperature', 273.15+temperature).density*1e-6;
    if nargin == 1
        density = density85+density87;
    else
        switch isotope
            case {'Rb85', '85Rb', '85'}
                density = density85;
            case {'Rb87', '87Rb', '87'}
                density = density87;
            otherwise
                error('Unkonwn isotope %s', isotope);
        end
    end     
end

